FAILURE MODES OF CONTINUOUS REINFORCED CONCRETE T-BEAMS STRENGTHENED USING CFRP LAMINATES

Yıl 2017, Sayı: 1, 286 - 303, 09.11.2017

Mohammad Mohie Eldin Ahmed M. Tarabia Rahma F. Hasson

Öz

Strengthening,
repairing and rehabilitation of existing structures are very important
functions of the construction industry nowadays. Laminates made of Carbon Fiber
Reinforced Polymers (CFRP) have proved an excellent behavior when used for the
strengthening, repairing and rehabilitation of existing structures. When CFRP
laminates are used to strengthen continuous reinforced concrete (RC) T-beams,
they may be fixed either in the lower soffit of the beam in the hogging moment
zone (HMZ); or in the upper surface of the beam, in the sagging moment zone
(SMZ) in the vicinity of mid-supports. Three types of failure modes may occur
in such structures; crushing of concrete, debonding between CFRP laminates and
concrete surfaces, and rupture of CFRP laminates. Each failure mode is
conducted according to a certain criterion which is a function of both
mechanical properties of materials (concrete, reinforcement, CFRP, and
adhesive) and dimensions of both RC beam and CFRP strengthening laminates. This
paper explains the sequence of occurring of the different failure modes of RC
continuous T-beams of two spans strengthened using CFRP laminates either in SMZ
or in HMZ. The paper contains the main details of the finite element (FE)
modeling process, behavior of the strengthened beams either in SMZ and HMZ and
the explanation of the different mechanisms of the failure modes of the
strengthened beams. Studied parameters include CFRP length, thickness, width
and locations of CFRP laminate across the flange of the studied T-beams. Also,
unstrengthened (control) beams were studied to compare the results with the
strengthened ones for better understanding of the effect of CFRP strengthening
upon the behavior of the studied T-beams. ANSYS which is a very powerful FE
tool is used to create 3-D models of this study. It was found that CFRP
dimensions are the principle factors that affect the type of the failure mode
occurred in the strengthened beam. Rupture occurs, only when strengthening of
the HMZ, if the CFRP stress reaches its maximum value (strength) by using very
small CFRP thickness comparing with the corresponding length. Debonding of CFRP
laminates occurs if shear stress, in the adhesive (contact) (bond layer)
between the laminate and the concrete, reaches its maximum value. Crushing of
concrete occurs as a final stage after yielding of steel reinforcement,
formation of a plastic hinge, moment redistribution till the capacity of the
beam is reached which means failure. 

Anahtar Kelimeler

ANSYS, CFRP, failure, rc beam, t-beam

Kaynakça

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